Interaction of H+ with the extracellular and intracellular aspects of hMATE1
Interaction of H+ with the extracellular and intracellular aspects of hMATE1
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DOI：
10.1152/ajprenal.00075.2011
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发表时间：
2011-09-01
影响因子：
4.2
通讯作者：
Wright, Stephen H.
中科院分区：
文献类型：
--
作者：
Dangprapai, Yodying;Wright, Stephen H.
DangPrapai Y，Wright SH.H+与hMATE1胞外和胞内的相互作用。Am J Physiol肾脏生理学301：F520-F528,2011。2011年5月25日首次发表；DOI：10.1152/ajprenal.00075.2011。-人类多药和毒素挤出1(HMATE1SLC47A1)是肾近端小管管腔膜有机阳离子/质子(OC/H+)交换活性的主要候选分子。尽管hMATE1的生理功能支持OC外流，但hMATE1介导的OC转运的动力学通常是通过摄取的测量来表征的，即面向外的hMATE1与OCS之间的相互作用。为了研究hMATE1介导的转运蛋白在更具生理学意义的方向上的动力学，即向内的hMATE1与细胞质底物之间的相互作用，我们从稳定表达该转运蛋白的中国仓鼠卵巢细胞中，测量了在不同的细胞内外pH条件下，hMATE1介导的原型底物[H-3]1-甲基-4-苯基吡啶外流的时间过程。在这项研究中，我们发现由常规摄取实验[12.9+/-1.23 nM(pH 7.89)；n=9]和外排法[14.7+/-3.45 nM(pH 7.83)；n=3]测定的胞外H+与外向hMATE1相互作用的IC50/K-I没有显著差异(P=0.6)。此外，用外排法测定细胞内H+与内向hMATE1相互作用的动力学表明，H+的IC50为11.5 nM(pH 7.91)，这与H+与hMATE1的内向和外向对称相互作用一致。
Dangprapai Y, Wright SH. Interaction of H+ with the extracellular and intracellular aspects of hMATE1. Am J Physiol Renal Physiol 301: F520-F528, 2011. First published May 25, 2011; doi:10.1152/ajprenal.00075.2011.- Human multidrug and toxin extrusion 1 (hMATE1, SLC47A1) is a major candidate for being the molecular identity of organic cation/proton (OC/H+) exchange activity in the luminal membrane of renal proximal tubules. Although physiological function of hMATE1 supports luminal OC efflux, the kinetics of hMATE1-mediated OC transport have typically been characterized through measurement of uptake, i.e., the interaction between outward-facing hMATE1 and OCs. To examine kinetics of hMATE1-mediated transport in a more physiologically relevant direction, i.e., an interaction between inward-facing hMATE1 and cytoplasmic substrates, we measured the time course of hMATE1-mediated efflux of the prototypic MATE1 substrate, [H-3] 1-methyl-4-phenylpyridinium, under a variety of intra-and extracellular pH conditions, from Chinese hamster ovary cells that stably expressed the transporter. In this study, we showed that an IC50/K-i for interaction between extracellular H+ and outward-facing hMATE1 determined from conventional uptake experiments [12.9 +/- 1.23 nM (pH 7.89); n = 9] and from the efflux protocol [14.7 +/- 3.45 nM (pH 7.83); n = 3] was not significantly different (P = 0.6). Furthermore, kinetics of interaction between intracellular H+ and inward-facing hMATE1 determined using the efflux protocol revealed an IC50 for H+ of 11.5 nM (pH 7.91), consistent with symmetrical interactions of H+ with the inward-facing and outward-facing aspects of hMATE1.